IF YOU’VE EVER TRIED to lose weight, bulk up, or change your body in any way, you know diet is seriously important—maybe even more important than exercise. For American Horror Story: Hotel star Matt Bomer, diet is “80 percent of how he maintains his body.” That’s what he told us during his interview for his Men’s Fitness cover story.

And the actor knows a thing or two about eating right. In fact, he’s studied the subject for more than 10 years. “When I was 27, I felt old. I didn’t feel right,” he said during the interview. “I didn’t feel healthy. I just wasn’t taking care of my body, and I had a body that wanted me to take care of it.” So he educated himself, pouring over books, talking to nutritionists and even going on a fasting retreat.

“In the end, someone is depending on me to show up on their set looking a specific way,” he said, “whether that’s 40 pounds overweight or 40 pounds underweight [which he did for his role in The Normal Heart, by consuming only the bare minimum of calories needed for survival], or looking like a stripper.”

But regardless of the inevitable extreme diet tweaks he makes to fit certain roles, there are some food rules of thumb he follows that are completely realistic for the average guy, too.